Network Metrics Requirements and Usage
for WP1
Tiziana Ferrari
Tiziana.Ferrari@cnaf.infn.it
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 1
Applicability examples
• Integration of network info into the scheduling policy:
– To define the most suitable Storage Element for one or more
Computing Elements
• Triggering of data transfers
– To gather in a single Storage Element portions of data sets
partioned among several Ses
• List of applications to be developed further…
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 2
Network information
• CloseSE attribute:
– CloseSE = {(closeness1, SE1), …, (closenessn, SEn)}
• closeness(CE, SE) = max 0
– Closeness varies in [0,1]
– 0 = SE unreachable
– 1 = SE on the same LAN
• Definitions
– r: Round Trip Time, Rmax: max RTT,
– ploss: packet loss frequency;
– th: throughput; thmax: maximum throughput
• closenessi,j (ploss ,r,th) = 0 if ploss 0
• closenessi,j (ploss ,r,th) = th / thmax r/ rmax where 0 < < 1
otherwise
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 3
Closeness i,j(p,th,r)
Fig 1: alpha = 1/2 Fig 2: alpha = 1/10
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 4
Triggering of data transfers
• Problem statement:
– Input data requested by a given job running on CE is partioned and
portions are stored in different SEi
– Input data needs to be gathered in a single SE and the most appropriate
one has to be selected
– Selection creteria:
• Amount of data in each SEi
• Network distance between two SE
• Closeness of SEi to CE under consideration
• SE is the selected Storage Element for acomputing element CE iff:
SE = SEi iff D(SEi) = minj D(SEj)
where D(SEi) is a SE Distance function.
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 5
SE Distance function D
• CASE 1: data in each SEi not known, SEi equivalently distant to CE
– D(SEi) = 1 j n, j i closeness(SEi , SEj )
• CASE 2: SEi equivalently distant to CE
– D(SEi) = max/ i * 1 j n, j i closeness(SEi , SEj )* max/ i
– i : amount of data in each Sei
– max: amount of data requested by a given job
• CASE 3:
– D(SEi) = closeness(CE, SEi) *max/ i * 1 j n, j i
closeness(SEi , SEj )
– : constant in ]0,1]
Tiziana Ferrari Network Metrics Requirements and Usage for WP1 6